Centrifugal pump



Oct. s, 1968 D. R. N|xoN CENTRIFUGAL PUMP Filed June e, 196e A ToRNEY A 4 j United States Patent O 3,404,631 CENTRIFUGAL PUMP Donald R. Nixon, Monroeville, Pitcairn, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed June 9, 1966, Ser. No. 556,338 8 Claims. (Cl. 10S-97) ABSTRACT OF THE DISCLOSURE A centrifugal pump having a centrifugal impeller within a housing, the housing having a closed upper portion and a lower end portion and an intermediate fluid outlet portion. The impeller has an imperforate lower end portion extending into the lower end portion of the housing and forming a suction inlet. The impeller also has a discharge outlet portion. The impeller is movable between positions of alignment and non-alignment of the fluid outlet and the discharge outlet. The lower impeller portion is movable into alignment with the fluid outlet forming a lluid flow barrier with the fluid outlet when the discharge outlet is out of alignment with the fluid outlet, the discharge being in alignment with the inner surface of the upper housing portion forming a fluid ow barrier with the suction inlet when the discharge outlet is in the position of non-align- ICC trifugal pump having varying flow rates in response to the position of the impeller within the pump chamber.

It is another object of this invention to provide a centrifugal pump by which the flow rate is controlled by changing the position of the impeller with respect to the casing.

It is another object of this invention to provide a centrifugal pump having a movable impeller by which the uid ow is varied and which concurrently prevents the liuid from bypassing the impeller.

Finally, it is an object of this invention to satisfy the foregoing problems and desiderata in a simple and expedient manner.

For a better understanding of the invention reference is made to the drawings, in which:

FIGURE l is a vertical sectional View, partly in elevation, of a centrifugal pump and showing alternate positions for the pump impeller and motor in broken lines; and

FIG. 2 is a vertical sectional view through a canned motor pump construction in which an alternate position of the impeller is shown in the broken lines.

Briefly, the present invention is directed to a centrifugal e pump of variable capacity including `a motor having a ment with the uid outlet. There are means for moving the impeller axially between said positions.

This invention relates to a centrifugal pump construction and more particularly it pertains to a pump impeller which is movable between open and closed positions for varying the pump capacity.

Ordinarily the output of a centrifugal pump is varied by changing the speed of rotation of the pump impeller or by throttling the discharge flow with a throttling valve. A variable speed prime mover is usually used to change impeller speed. For some applications, however, it is cheaper and more desirable to use a constant speed motor. Bearing design is a difiiculty frequently encountered with variable speed motors. At low speeds, there may be diiculty in maintaining a bearing lm such as for hydrodynamic `bearings. Thus, where a constant high speed motor is used the problem of bearing design is simplified.

Moreover, in certain applications the speed of the pump is controlled by elaborate and expensive auxiliary equipment which is only necessary during the startup but which must be housed and maintained at all times. Such equipment includes liquid rheostats, eddy current couplings, and the like.

Associated with the foregoing has been a special problem involving the pumping of a liquid metal such as sodium. Large flow control valves for that purpose have not yet been developed successfully.

In accordance with the present invention it has been found that the foregoing problems may be overcome by controlling the flow of the liquid being pumped while the pump shaft rotates at full speed by changing the position of the impeller discharge passages with respect to the pump casing. Indeed, the output of the pump may be varied from 100% to substantially zero by adjusting the position of the impeller with respect to the pump outlet port. At the same time, means are provided for closing the inlet port to prevent the fluid ow through the pump. Thus, a check valve is not required to prevent flow through this pump when it is stopped and other pumps are running in parallel piping.

Accordingly, it is a general object of this invention to provide a centrifugal pump having a pump impeller which is movable into and out of the pumping chamber.

It is another object of this invention to provide a censhaft, a pump housing having tubular Walls forming an elongated chamber of circular cross section, the tubular walls including upper and lower end portions and an intermediate enlarged annular portion that is communicative with the elongated chamber, the lower end portion of the housing providing an axial fluid inlet and the intermediate enlarged annular portion having a fluid outlet, the motor being disposed at one end of the housing and the shaft extending into the chamber and axially thereof, a pump impeller on the shaft and within the housing and rotatable and slidable therein, the impeller having an upper end portion and a lower cylindrical portion telescopically disposed within the lower end portion of the tubular walls, the impeller also having an intermediate portion including a plurality of spaced impeller blades extending radially outwardly and being disposed between the upper hub portion and the lower cylindrical portion, the impeller blades forming fluid passages communicating with the intermediate enlarged annular portion of the chamber, the impeller and housing being longitudinally movable with respect to each other between pumping and non-pumping positions the pumping position corresponding to the position of the impeller intermediate portions being aligned with the er1- larged annular portion of the housing and the non-pumping position corresponding to the intermediate portion of the impeller being located in the upper end portion of the housing and with the lower end portion of the impeller being aligned with the enlarged annular portion of the housing to block bypass fluid flow, and means for moving one of the impeller and housing longitudinally with respect to each other between the pumping and non-pumping positions.

In FIG. l, a motor pump unit is shown and includes a pump 10, a motor 12, a drive shaft 14 leading from the motor to the pump, and motor lifting means generally indicated at 16. The pump portion 10 includes a housing 18 and centrifugal impeller 20 which is secured to the lower end of the drive shaft 14.

The housing 18 is an elongated tubular member which forms an inner chamber 22 of 'circular cross section the center of which is preferably axially disposed with respect to the axis of the drive shaft 14, and of the impeller 20. More particularly, the housing 18 includes a closed upper tubular portion 24 4and enlarged intermediate portion 26, and a lower cylindrical portion 28.

As shown in FIG. l, the several portions 24, 26 and 28 are integral and may be disposed at the lower end of an elongated shaft housing the upper end of which has a mounting flange 32 that is secured to a base 34. The upper end of the tubular portion 24 has a shoulder 36 and is an upper end Wall for the chamber 22 which Wall has a central opening 38 for the bore of the shaft housing 30.

The intermediate portion 26 of the housing 18 provides an enlarged annular chamber 40 for confining the uid being pumped as it is driven by centrifugal force from the impeller 20. The enlarged chamber 40 is provided with an outlet 42 for the fluid in the periphery of the chamber formed by the intermediate portion 26 of the housing.

The lower cylindrical portion 28 of the housing encloses the lower portion of the housing chamber 22 which is preferably cylindrical and of circular cross section and extends for a considerable distance below the enlarged annular portion 40 of the chamber.

The impeller 20 includes an upper end member 44 and a lower cylindrical portion 46 having imperforate side walls. The outer periphery of the impeller 20 is preferably circular with the upper end member 44 having a diameter slightly less than that of the chamber 22 as defined by the upper tubular portion 24 of the housing. The lower portion 46 of the impeller has an outer diameter slightly less than that of the lower portion of the chamber 22 and fits telescopically within the lower cylindrical portion 28 of the housing. An annular bearing and sealing unit 48 is provided between the members 28 and 46 to permit rotation and longitudinal sliding therebetween. The lower cylindrical portion 46 of the impeller 20 forms an inner conduit 50 which Serves as an inlet for the uid being pumped.

The impeller 20 includes an intermediate portion having a plurality of pallets or impeller blades 52 which extend substantially longitudinally between and are secured to the upper end member 44 and the lower cylindrical portion 46 of the impeller. Moreover, the blades S2 extend radially outwardly from inner edges 54 (at the upper end of the conduit 50) two outer edges 56. The blades 52 provide a plurality of radially extending fluid passages 58 and -communicate between the conduit 50 and the enlarged annular chamber 40.

Thus, a uid being pumped entering the lower end of the pump housing as indicated by the arrow 60 moves upwardly through the conduit 50 to the radially extending passages 58 as indicated by the arrows 62, and thence into the annular chamber 40 from where the fluid exits through the fluid outlet 42 as indicated by the arrow 64. As shown in FIG. l, the impeller 20 is secured to the lower end of the drive shaft 14 and is thereby rotated by the motor 12. A bearing and seal unit 66 is provided between the ange 32 and the shaft 14.

The lifting means 16 for the motor may be of any suitable construction such as pneumatic, hydraulic or mechanical, the latter of which may include a plurality of motors 68 which operate a worm gear assembly 70 for turning screws 72 at the upper ends of which a motor mounting plate 74 is provided.

In operation, the impeller 20 is normally disposed in the position shown in FIG. 1 with the blades 52 and fiuid passages therebetween 58 aligned with the annular chamber portion 40 whereby all of the liquid being pumped passes directly into the annular chamber in an uninhibited manner due to centrifugal force applied by the impeller 20. When it is necessary to reduce the flow of liquid through the pump, the impeller 20 is raised partially or completely into the upper tubular portion 24 of the housing as indicated by the broken line 76. As the impeller 20 is raised from the lower to the upper position, the passages 58 are raised out of alignment with the annular chamber 4t) and into juxtaposition with the inner surface of the upper housing portion 24 which acts a barrier against radial fiow of the liquid being pumped.

At the same time, the lower cylindrical portion 46 of the impeller raises a corresponding amount and is radially aligned with the enlarged annular chamber 40 to block the liquid from flowing through the conduit 50 into the chamber 40 in bypassing relationship `with impeller 20. The uppermost position of the motor 12 is indicated by the broken lines 78.

Another embodiment of the invention is shown in FIG. 2 in which a sealed or canned motor pump unit is shown. The unit includes a pump 80, a motor 82, a shaft 84 and lifting means 86. The pump includes a housing 88, a centrifugal impeller which is disposed in a tubular member 92, all of which members 88, 90 and 92 are substantially identical to the members 18, 20 and 22 respectively of the pump shown in FIG. 1. Inasmuch as both pumps 10 and 80 are constructed and operate in a similar manner no further description of the construction and operation of the pump 80 is included.

The primary difference between the unit of FIG. 1 and of FIG. 2 is in the motor 80 and lifting means. The motor 82 is enclosed within an outer cylindrical housing 94 and includes an annular stator 96, a squirrel cage rotor 98, and a rotor chamber 100. The upper end of the shaft 84 includes a ange 102 of circular cross section in the undersurface of which is disposed an annular bearing 104. The shaft 84 is mounted in upper and lower radial bearings 106 and 108.

The llifting means 86 includes a yoke 110 having downturned members 112 at the lower ends of which is mounted an annular plate 114, The members 112 are vertically grooved at 116 for engagement with a pair of radially spaced splines 118 to prevent rotation of the lifting means 86, but to permit longitudinal movement of the means 86 toward an upper end wall 120 of the housing 94. The annular plate 114 supports a number of spaced thrust shoes 122 and links 124 which shoes engage the undersurface of the annular bearing 104 to lift the rotor 98 on the shaft 84 upwardly to the broken line position 126. The upper limits of the lifting means 86 is indicated by the broken line 128. When the rotor 98 is lifted to the position 126, the impeller 90 is raised to the broken line position 130 at the upper end of the pump chamber 92, thereby reducing the output of the pump to a minimum.

The lifting means 86 also includes a rod 132 extending upwardly from the yoke and having an upper threaded portion 134 which is engaged Iby an annular nut 136. The nut 136 is journaled in bearings 138 at the upper portion of a frame 140. The lifting means 86 also includes a motor 142 and a worm and Worm gear assembly 144 cooperatively connected with the nut 136 for rotating the same in reversible directions.

Due to the relatively high pressures developed in the pump chamber formed by the tubular member 92, the fluid being pumped seeps into and fills the rotor chamber and immerses the upper and lower bearings 106 and 108. Moreover, the uid immerses the parts forming the lifting means 86. The stator 96 is sealed from the fluid in the rotor chamber by a cylindrical can or sleeve 148 having upper and lower ends sealed in a fluid-tight manner such as by welds 150 and 152. Additional sealing means such as bellows 146 is provided between the upper end wall and the thread portion 134 as a hermetic seal between the rod and the housing end wall 120 to prevent the fluid from leaking into the atmosphere.

Accordingly, the device of the present invention provides a pump by which the flow rate can be controlled by changing the position of the impeller with respect to the pump casing. The device is devoid of the usual throttle valves or means for varying the speed of the pump shaft which have often involved elaborate, expensive and unreliable auxiliary equipment. The device of the present invention permits 100% control of the ow while the pump shaft rotates at full speed by simply changing the position of the impeller discharge passages with respect to the pump housing. By raising the impeller completely into a shut-off chamber the system flow is essentially zero. By lowering the impeller the flow may be gradually increased to the maximum flow rate. Thus, the device of the present invention satisfies many disadvantages inherent in prior existing centrifugal pumps.

Moreover, the device of the present invention provides a variable capacity centrifugal pump operated by a constant speed motor. The pump impeller has an elongated cylindrical ange that is pulled into the pumping position of the impeller blades when the latter are moved to a non-pumping position. Thus, the impeller provides a positive means for blocking passage of uid through the pump where the impeller blades are in the inoperative position.

It is understood that the above specification and drawings are merely exemplary and not in limitation of the invention.

What is claimed is:

1. A centrifugal pump comprising a housing and a centrifugal impeller within the housing, the housing having walls forming a tubular chamber having a closed upper portion and a lower end portion and forming a iluid outlet intermediate of the upper and lower end portions, the impeller having a lower portion with imperforate side walls extending into the lower end portion of the housing, the impeller also having a suction inlet in the lower portion and having a discharge outlet alignable with the fluid outlet in the housing, one of the housing and the impeller being movable between positions of alignment and non-alignment of the fluid outlet and the discharge outlet, the lower impeller portion being movable so as to bring the imperforate side walls into alignment with the fluid outlet thereby forming a fluid bypass flow barrier with respect to the fluid outlet when the discharge outlet is positioned out of alignment with the uid outlet, the discharge outlet portion of the impeller being in alignment with the inner surface of the closed upper portion of the housing thereby forming a fluid liow barrier with respect to the suction inlet when the discharge outlet is positioned out of alignment with the fluid outlet, and means for moving one of the housing and the impeller axially between said positions.

2. The pump of4 claim 1 in which the lower impeller portion is cylindrical and is telescopically disposed within the lower end portion.

3. The pump of claim 1 in which the impeller is movable with respect to the housing.

4. The pump of claim 1 in which the discharge outlet of the impeller is snugly disposed within the upper end portion of the housing when the impeller lower end portion is aligned with the iiuid outlet.

5. The pump of claim 1 in which means for rotating the impeller are provided which means includes a motor having a shaft which extends into the upper end portion of the housing, and in which the impeller is attached to the end of the shaft.

6. The pump of claim 5 in which the moving means is operatively connected to the motor.

7. The pump of claim 1 in which means for rotating the impeller are provided which means includes a motor having a rotor with shaft extensions at both ends, a tubular motor housing containing a stator having an opening in which the rotor is mounted, means hermetically enclosing the stator in the housing, one of the shaft eXtensions extending into the tubular chamber, the impeller being mounted on the end of the shaft, and the means for moving one of the housing and the impeller being attached to the other shaft extension for moving the impeller within the tubular chamber.

8. The pump of claim 5 in which the lower impeller portion is cylindrical and is telescopically disposed within the lower end portion, and in which the suction inlet of the impeller is disposed within the lower cylindrical portion.

References Cited UNITED STATES PATENTS 1,433,037 10/ 1922 Reid. 3,162,128 12/1964 Horlen 103-97 XR 3,167,021 1/1965 Sence 1,03-97 XR ROBERT M. WALKER, Prmmy Examiner. 

